Location apparatus

ABSTRACT

A difference between a received wave and a convolution operation result is calculated by a difference calculating section, the convolution operation result being obtained by carrying out a convolution operation based upon operation results output from impulse response operating sections (1 0 )(1 1 ) . . . (1 n ) which employ a peak value of each pulse as a multiplier and employ an estimated value of an unknown impulse response as a multiplicand, each pulse being obtained by obtaining a pulse train based upon a radiating waveform. The estimated impulse responses are corrected by correcting sections (1 0a )(1 1a ) . . . (1 na ) of the impulse response operating sections (1 0 )(1 1 ) . . . (1 n ) based upon the calculated difference. And the corrected estimated impulse responses are supplied to the impulse response operating section at the next stage. Location with high discrimination and with real time processing, and enlargement in locating extent with keeping high discrimination are performed by carrying out these processings.

SPECIFICATION

1. Technical Field

The present invention relates to a location apparatus. Moreparticularly, the present invention relates to a location apparatusdepending upon a principal which is coincident to a principal of a pulseecho method, the location apparatus being represented by sonic locationusing an ultrasonic wave.

2. Background Art

From the past years, a so called pulse echo method is widely known,which method measures a location on a boundary face at which a densityof the medium varies, based upon an intensity of pulse echoes, byperiodically radiating an ultrasonic pulse from a wave radiating point91 and by receiving pulse echoes at wave receiving points 93, the pulseecho being reflected by a reflector 92 and coming back, as isillustrated in FIG. 3.

In recent years, an ultrasonic tomograph, among other non-invasionmeasuring devices for medical use,has been extremely spread and hasgreatly contributed to improvement in accuracy of diagnosis. Anoperation principal of an ultrasonic diagnosing apparatus which isrepresented by an ultrasonic tomograph, is the same as a pulse echomethod which is widely known as a principal of active sonar. Wherein, amode for observing a time waveform of intensity of a reflected wave, iscalled an A-mode (refer to FIG. 4), a mode for observing a twodimensional image which is in a depth direction and in a scanningdirection by scanning a probe one dimensionally and by determining athreshold value, is called a B-mode (refer to FIG. 5), and a mode forobserving a two dimensional image, each point of the image being at anequal depth one another, by performing the scanning two dimensionally,is called a C-mode (refer to FIG. 6).

Therefore, diagnosis of the interior of a human body can be performedwithout injuring the human body, by employing the ultrasonic diagnosingapparatus and by selecting the A-mode, B-mode or C-mode corresponding tothe species of the objected diagnosis.

By employing an ultrasonic flaw detecting apparatus based upon thesimilar principal as of the foregoing, various structures can be checkedto determine whether or not cracks exist in the interior thereof and thelike. The abovementioned ultrasonic diagnosing apparatus has a spacialdiscrimination of about 5 mm, which is too low in comparison with aspacial discrimination (about 1 mm) required for usage of earlydetection of cancer and the like, therefore a disadvantage arises inthat the abovementioned ultrasonic diagnosing apparatus cannot beapplied to usage of early detection of cancer and the like.

It is thought that a length of a burst wave of a radiating ultrasonicwave is shortened for the purpose of improving spacial discrimination(improving resolution). Specifically, it is generally selected toaccomplish this by shortening a burst wave by selecting a high frequencyas a frequency of a radiating ultrasonic pulse, because a burst waveformcan easily be shortened by raising a frequency of an ultrasound. But,when the frequency is raised, attenuation of a ultrasound becomesremarkable, and a new disadvantage arises in that an ultrasound having ahigh frequency cannot be applied to diagnosing a deep portion of a humanbody. It is thought that a probe which can output a short burst waveformcan be employed for shortening the burst waveform without raising afrequency. But, development of a new probe requires research of materialby trial and error, and a disadvantage arises in that the developmentrequires a long time period. Thereby, a new probe cannot be appliedimmediately in the present condition.

Further, it is known as a method for improving spacial discriminationwithout raising a frequency of an ultrasonic pulse, that an impulseresponse is obtained by performing fast Fourier transformation operation(hereinafter referred to as FFT operation) based upon a radiatingwaveform and received waveform. But, disadvantages arise in that alimitation exists which requires a sampling number of data by 2^(N), inthat operating apparatus becomes large in size, and in that real timeobtaining is eliminated. Therefore, the FFT is scarcely used fordiagnosis of a human body which makes much account of real timeobtaining.

In the foregoing, only a searching method of an ultrasonic diagnosisapparatus is described, similar disadvantages as the above-mentioneddisadvantages arise in an ultrasonic flaw detecting apparatus, a radarand the like.

The present invention was made to solve the above-mentioned problems.

It is an object of the present invention to supply a novel locationapparatus which can improve spacial discrimination without varying aradiating wave, and which can perform real time location.

Disclosure of The Invention

To perform the object above-mentioned, a location apparatus according toclaim 1 of the present invention includes;

pulse train recording means for recording a radiating wave as pluralpulse trains,

impulse response operating means for performing operations based uponcorresponding impulse responses which are assigned to each pulse and apredetermined value, and for influencing the corresponding impulseresponse of the operation corresponding to a next pulse,

convolution operating means for the operation results, the convolutionoperating means performing convolution operations of operation resultsobtained by each impulse response operating means,

difference calculating means for calculating a difference between theconvolution operation result and a received wave, and

correcting means for correcting the impulse response in each impulseresponse operating means based upon a calculated difference.

The impulse response operating means may include the pulse trainrecording means and the correcting means therein.

As to the location apparatus according to claim 1, the radiating wave isrecorded by the pulse train recording means as plural pulse trains, andthe operations are performed by the impulse response operating meansbased upon corresponding impulse responses which are assigned to eachpulse and a predetermined value. The operation corresponding to a nextpulse is influenced by the operation result from the impulse responseoperating means, when a location on a boundary face at which a densityof a medium varies based upon a received wave which is obtained byradiating a radiating wave and by receiving a reflected wave. And, theoperation result obtained by each impulse response operating means isconvolution operated by the convolution operating means for operationresults, the difference between the convolution operation result and thereceived wave is calculated by the difference calculating means, theimpulse response in each impulse response operating means beingcorrected based upon the calculated difference by the correcting means.Accordingly, high spacial descrimination can be performed without usinga special wave radiating device and wave receiving device. Enlargementof locating extent and raising of spacial descrimination can beperformed by lowering the pulse frequency of the radiating wave and byraising a sampling rate of the received wave, even when the materialbeing examined has a great attenuating rate in a high frequency band.Further, the impulse response can be obtained in real time which isdifferent from the FFT processing.

A location apparatus according to claim 2 of the present inventionfurther includes;

preceding received wave pulse outputting means for outputting a receivedwave pulse which precedes a current received wave pulse,

convolution operating means for operation results which correspond to apreceding received wave,

difference calculating means which correspond to a preceding receivedwave, and

convolution operating means for convolution operating a differenceobtained by the corresponding difference calculating means, and forsupplying a convolution operation result to the correcting means incorrespondence to each impulse response operating means.

As to the location apparatus according to claim 2 of the presentinvention, resistance to noises is raised, therefore the location on theboundary face at which a density of the medium varies, can be measuredwith high accuracy, because the impulse response is corrected by takingnot only the received wave at the present time but also the precedingreceived wave into consideration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a main portion of an acousticlocation apparatus as an embodiment of a location apparatus according tothe present invention,

FIG. 2 is a block diagram illustrating a main portion of an acousticlocation apparatus as another embodiment of a location apparatusaccording to the present invention,

FIG. 3 is a schematic diagram for explaining a principal of a pulse echomethod,

FIG. 4 is a schematic diagram for explaining a mode for observing a timewaveform of intensity of a reflected wave,

FIG. 5 is a schematic diagram for explaining a mode for observing a twodimensional image which is in a depth direction and in a scanningdirection by scanning a probe one dimensionally and by determining athreshold value, and

FIG. 6 is a schematic diagram for explaining a mode for observing a twodimensional image, each point of the image being at an equal depth oneanother, by performing the scanning two dimensionally.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, referring to the attached drawings, we explain the presentinvention in detail.

FIG. 1 is a block diagram illustrating a main portion of an ultrasoniclocation apparatus as an embodiment of a location apparatus according tothe present invention.

The ultrasonic location apparatus includes;

impulse response operating sections 1₀, 1₁, . . . , 1_(n) for performingoperations in which a peak value x₀, x₁, . . . x_(n) of each pulse, whenan ultrasonic wave which is radiated from a wave radiating device andhas a predetermined frequency, is determined as a multiplier, and animpulse response g_(j), g.sub.(j-1), . . . ,g.sub.(j-n) to be estimatedis determined as a multiplicand,

a convolution operating section 2 for performing convolution operationsbased upon the operation results output from all impulse responseoperating sections,

a difference calculating section 3 for receiving the convolutionoperation result and the received wave pulse obtained by sampling awaveform of a received wave at a predetermined sampling Fate, and forcalculating a difference between the both, and

a random number generating device 4 for giving a virtual initial valuefor an unknown impulse response g_(j) to the impulse response operatingsection 1₀ at the first stage.

The impulse response operating sections 1₀, 1₁, . . . , 1_(n) havecorrecting sections 1_(0a), 1_(1a), . . . , 1_(na) for correctingcorresponding impulse responses based upon the above-mentioneddifference, and each impulse response operating section supplies theimpulse response corrected by each correcting section to the impulseresponse operating section of the next stage. The impulse responsecorrected by the correcting section 1_(na) of the last stage is outputas an ultrasonic locating result.

More specifically, when an impulse response of a boundary face at time 3is expressed by G_(j), a measured reflected wave (received wave) isexpressed by Y_(j), and a sound pressure of the radiated ultrasonicpulse is small and satisfy linear addition, the received wave y_(j) canbe expressed by the following equation, because a peak value x(τ) ofeach pulse of the radiating ultrasonic wave is x₀, x₁, . . . ,x_(n).##EQU1##

Therefore, when an accurate impulse response is determined in eachimpulse response operating section, the convolution operation resultO_(j) (refer to the next equation) coincides with the received wavey_(j), and the difference y_(j) -O_(j) output from the differencecalculating section 3 for operation result, becomes 0. ##EQU2##

But, a case scarcely exists in which accurate impulse responses aredetermined for all impulse response operating sections actually, andnoises are mixed when measuring is performed. Therefore, the differencey_(j) -O_(j) corresponding to a shift between the estimated impulseresponse g.sub.(j-i) and the actual impulse response G.sub.(j-i), isoutput from the difference calculating section 3 for operation result.

Then, the estimated impulse response is corrected by performing thecorrecting operation, which is indicated by the following equation,based upon the difference y_(j) -O_(j) output from the differencecalculating section 3 for operation result, in the correcting sectionwhich is included in each impulse response operating section.

    g.sub.(j-i) =g.sub.(j-i) +ε·(y.sub.j -O.sub.j)·x.sub.i

Wherein, ε is a parameter which influences a convergence speed andstability of an impulse response, and is determined by an extremelysmall positive value.

Therefore, the estimated impulse response comes nearer to the actualimpulse response G.sub.(j-i) by a correction value based upon theabove-mentioned correcting operation. The corrected impulse response issupplied to the impulse response operating section of the next stage soas to correspond to the processing at the next time, then a processingsimilar to the above-mentioned processing is repetitively performed.

As a result, the impulse response g.sub.(j-i) which can be approximatedwith high accuracy to the actual impulse response G.sub.(j-i), isobtained by sequentially performing the above-mentioned processings inthe impulse response operating sections 1₀, 1₁, . . . ,1_(n).

As is apparent from the foregoing, after the impulse response correctingprocessings of n-number of stages are performed, the impulse responsecan instantaneously be obtained at every obtaining of data, thereby realtime processing can be realized. The location apparatus can easily beraised in resolution by lowering the frequency of the radiating wave soas to decrease attenuating thereof and by raising the sampling rate forobtaining a data train.

Second Embodiment

FIG. 2 is a block diagram illustrating a main portion of an acousticlocation apparatus as another embodiment of a location apparatusaccording to the present invention.

The acoustic location apparatus differs from the embodiment of FIG. 1 inthat convolution operating sections 2a, 2b and difference calculatingsections 3a, 3b for operation results are further provided other thanthe convolution operating section 2 and the difference calculatingsection 3 for operation result, in that delay circuitries 5a, 5b areprovided for supplying the received wave to the difference calculatingsections 3a, 3b for operation result under the condition that thereceived wave are delayed by a predetermined time period, in thatimpulse response operating sections 1_(n+1), 1₁₊₂ are further providedand in that convolution operating sections 6₀, 6₁, . . . , 6_(n),6_(n+1), 6_(n+2) are provided corresponding to each impulse responseoperating section, so as to supply the operation result output from theconvolution operating section to the correcting section included in thecorresponding impulse response operating section.

And, the operation results output from the impulse response operatingsections 1₀, 1₁, . . . ,1_(n) are supplied to the convolution operatingsection 2, the operation results output from the impulse responseoperating sections 1₁, 1₂, . . . ,1_(n), 1_(n+1) are supplied to theconvolution operating section 2a for operation result, and the operationresults output from the impulse response operating sections 1₂, 1₃, . .. ,1_(n), 1_(n+1), 1_(n+2) are supplied to the convolution operatingsection 2a for operation result. And, the difference output from thedifference calculating section 3 for operation result is supplied to theconvolution operating sections 6₀, 6₁, . . . , 6_(n) for difference, thedifference output from the difference calculating section 3a foroperation result is supplied to the convolution operating sections 6₁,6₂, . . . , 6_(n), 6_(n+1) for difference, and the difference outputfrom the difference calculating section 3b for operation result issupplied to the convolution operating sections 6₂, 6₃, . . . , 6_(n),6_(n+1), 6_(n+2) for difference.

Thetrefore, in this embodiment, a difference is calculated by eachconvolution operating section for operation result and differencecalculating section as similar as of the first embodiment. As a result,the difference d_(j) =y_(j) -O_(j) at time j, the difference d_(j-1)=y_(j-1) -O_(j-1) at time j-1, and the difference d_(j-2) =y_(j-2)-O_(j-2) at time j-2 are obtained simultaneously. These differences aresupplied to corresponding convolution operating section for difference,respectively, and the operation results output from the convolutionoperating sections for difference are supplied to the correcting sectionof the corresponding impulse response operating section, respectively.Wherein, the convolution operating section 6_(i) (i=2, 3, . . . , n) isdetermined weighting factors x_(i), x_(i+1), x_(i+2) corresponding tothe differences d_(j), d_(j-1), d_(j-2) output from the differencecalculating sections 3, 3a, 3b. The convolution operating section 6_(i)performs a convolution operation of x_(i) ·d_(j) +x_(i+1) ·d_(j-1)+x_(i+2) ·d_(j-2) so as to obtain an operation result, and supplies theoperation result to the correcting section of the corresponding impulseresponse operating section. The convolution operating section 6₀determines a weighting factor x₀ corresponding to the difference d_(j)output from the difference calculating sections 3. The convolutionoperating section 6₀ performs a convolution operation of x₀ ·d_(j) so asto obtain an operation result, and supplies the operation result to thecorrecting section of the corresponding impulse response operatingsection. The convolution operating section 6₁ determines weightingfactors x₀, x₁ corresponding to the differences d_(j), d_(j-1) outputfrom the difference calculating sections 3, 3a. The convolutionoperating section 6₁ performs a convolution operation of x₀ ·d_(j) +x₁·d_(j-1) so as to obtain an operation result, and supplies the operationresult to the correcting section of the corresponding impulse responseoperating section. The convolution operating section 6_(n+1) determinesweighting factors x_(n-1), x_(n) corresponding to the differencesd_(j-1), d_(j-2) output from the difference calculating sections 3a, 3b.The convolution operating section 6_(n+1) performs a convolutionoperation of x_(n) ·d_(j-1) +x_(n-1) ·d_(j-2) so as to obtain anoperation result, and supplies the operation result to the correctingsection of the corresponding impulse response operating section. Theconvolution operating section 6_(n+2) determines a weighting factorx_(n) corresponding to the difference d_(j-2) output from the differencecalculating sections 3b. The convolution operating section 6_(n+2)performs a convolution operation of x_(n) ·d_(j-) 2 so as to obtain anoperation result, and supplies the operation result to the correctingsection of the corresponding impulse response operating section.

Differences corresponding not only to the received wave at time j butalso to the received waves at time j-1 and j-2 are obtained, impulseresponses are corrected by the correcting sections based upon allobtained differences, and each corrected impulse response is supplied tothe impulse response operating sections of the next stage, then theprocessing similar to the processing above-mentioned is repetitivelyperformed. Therefore, ultrasonic location with high accuracy can beperformed, because influence by noises is greatly reduced even whennoises are mixed instantaneously to the received wave.

In the second embodiment, impulse responses are estimated by taking thereceived waves at time j, j-1 and j-2 into consideration, but it ispossible that the resistance to noises can further be raised byincreasing the timings of the received waves which are to be taken intoconsideration.

The present invention is not limited to the above-mentioned embodiments.

The present invention is applicable to various fields such as anultrasonic diagnosis apparatus, sonar, radar and the like.

The present invention can be applied various modifications within anextent in which the scope of the present invention is not changed.

As is apparent from the foregoing, the location apparatus according tothe present invention can achieve high spacial discrimination withoutusing a special wave radiating device and wave receiving device. Thelocation apparatus can enlarge a locating extent and can raise spacialdiscrimination by lowering a pulse frequency of a radiating wave and byraising a sampling rate of a received wave. The location apparatus canobtain impulse responses in real time which is different from the FFTprocessing. The location apparatus is preferable to an ultrasoniclocation apparatus, ultrasonic diagnosis apparatus, sonar, radar and thelike.

What is claimed:
 1. A location apparatus for measuring a location of aboundary face by radiating a radiating wave at the boundary face and byreceiving a received wave reflected from the boundary face, the locationapparatus comprising:pulse train recording means for recording aradiating wave as plural pulses in a pulse train, a plurality of impulseresponse operating means for performing operations based upon acorresponding impulse response, each of the impulse response operatingmeans being associated with one of the plural pulses, first convolutionoperating means for performing convolution operations upon operationresults obtained by each of the impulse response operating means, firstdifference calculating means for calculating a difference between aconvolution operation result from the first convolution operation meansand a current received wave, and correcting means associated with eachimpulse response operating means for correcting the impulse response inthe associated impulse response operating means based upon thedifference calculated by the difference calculating means, the correctedimpulse response for at least one of the plurality of impulse responseoperating means being provided to another of the plurality of theimpulse response operating means.
 2. A location apparatus as set forthin claim 1, further including;preceding received wave outputting meansfor outputting a preceding received wave which precedes a currentreceived wave, second convolution operating means for convolutionoperating operation results which correspond to the preceding receivedwave, second difference calculating means, for calculating a differencebetween a convolution operation result from the second convolutionoperation means and third convolution operating means for convolutionoperating a difference obtained one or both of the first and seconddifference calculating means, and for supplying a convolution operationresult to the correcting means corresponding to each impulse responseoperating means.